diff --git a/include/common/ttypes.h b/include/common/ttypes.h
index 3602b045a9..16c59465cc 100644
--- a/include/common/ttypes.h
+++ b/include/common/ttypes.h
@@ -180,8 +180,11 @@ typedef struct {
     }                                                                                  \
   } while (0)
 
-// TODO: use varchar(0) to represent NULL type
+
+//TODO: use varchar(0) to represent NULL type
+#define IS_VAR_NULL_TYPE(_t, _b)     ((_t) == TSDB_DATA_TYPE_VARCHAR && (_b) == 0)
 #define IS_NULL_TYPE(_t)             ((_t) == TSDB_DATA_TYPE_NULL)
+
 #define IS_SIGNED_NUMERIC_TYPE(_t)   ((_t) >= TSDB_DATA_TYPE_TINYINT && (_t) <= TSDB_DATA_TYPE_BIGINT)
 #define IS_UNSIGNED_NUMERIC_TYPE(_t) ((_t) >= TSDB_DATA_TYPE_UTINYINT && (_t) <= TSDB_DATA_TYPE_UBIGINT)
 #define IS_FLOAT_TYPE(_t)            ((_t) == TSDB_DATA_TYPE_FLOAT || (_t) == TSDB_DATA_TYPE_DOUBLE)
diff --git a/source/client/src/clientImpl.c b/source/client/src/clientImpl.c
index e7b4fb0657..0f0cf064d6 100644
--- a/source/client/src/clientImpl.c
+++ b/source/client/src/clientImpl.c
@@ -923,7 +923,7 @@ void doSetOneRowPtr(SReqResultInfo* pResultInfo) {
     int32_t bytes = pResultInfo->fields[i].bytes;
 
     if (IS_VAR_DATA_TYPE(type)) {
-      if (pCol->offset[pResultInfo->current] != -1) {
+      if (!IS_VAR_NULL_TYPE(type, bytes) && pCol->offset[pResultInfo->current] != -1) {
         char* pStart = pResultInfo->pCol[i].offset[pResultInfo->current] + pResultInfo->pCol[i].pData;
 
         pResultInfo->length[i] = varDataLen(pStart);
diff --git a/source/libs/function/src/builtins.c b/source/libs/function/src/builtins.c
index 5d69cc6189..c9c63169c9 100644
--- a/source/libs/function/src/builtins.c
+++ b/source/libs/function/src/builtins.c
@@ -846,7 +846,7 @@ static int32_t translateConcatImpl(SFunctionNode* pFunc, char* pErrBuf, int32_t
   for (int32_t i = 0; i < numOfParams; ++i) {
     SNode*  pPara = nodesListGetNode(pFunc->pParameterList, i);
     uint8_t paraType = ((SExprNode*)pPara)->resType.type;
-    if (!IS_VAR_DATA_TYPE(paraType) && TSDB_DATA_TYPE_NULL != paraType) {
+    if (!IS_VAR_DATA_TYPE(paraType) && !IS_NULL_TYPE(paraType)) {
       return invaildFuncParaTypeErrMsg(pErrBuf, len, pFunc->functionName);
     }
     if (TSDB_DATA_TYPE_NCHAR == paraType) {
@@ -859,6 +859,12 @@ static int32_t translateConcatImpl(SFunctionNode* pFunc, char* pErrBuf, int32_t
     uint8_t paraType = ((SExprNode*)pPara)->resType.type;
     int32_t paraBytes = ((SExprNode*)pPara)->resType.bytes;
     int32_t factor = 1;
+    if (IS_NULL_TYPE(paraType)) {
+      resultType = TSDB_DATA_TYPE_VARCHAR;
+      resultBytes = 0;
+      sepBytes = 0;
+      break;
+    }
     if (TSDB_DATA_TYPE_NCHAR == resultType && TSDB_DATA_TYPE_VARCHAR == paraType) {
       factor *= TSDB_NCHAR_SIZE;
     }
diff --git a/source/libs/scalar/src/sclfunc.c b/source/libs/scalar/src/sclfunc.c
index 370ea8fa2e..587f9b5515 100644
--- a/source/libs/scalar/src/sclfunc.c
+++ b/source/libs/scalar/src/sclfunc.c
@@ -449,7 +449,7 @@ int32_t concatFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOu
     bool hasNull = false;
     for (int32_t i = 0; i < inputNum; ++i) {
       if (colDataIsNull_s(pInputData[i], k) ||
-          GET_PARAM_TYPE(&pInput[i]) == TSDB_DATA_TYPE_NULL) {
+          IS_NULL_TYPE(GET_PARAM_TYPE(&pInput[i]))) {
         colDataAppendNULL(pOutputData, k);
         hasNull = true;
         break;
@@ -526,7 +526,7 @@ int32_t concatWsFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *p
 
   for (int32_t k = 0; k < numOfRows; ++k) {
     if (colDataIsNull_s(pInputData[0], k) ||
-        GET_PARAM_TYPE(&pInput[0]) == TSDB_DATA_TYPE_NULL) {
+        IS_NULL_TYPE(GET_PARAM_TYPE(&pInput[0]))) {
       colDataAppendNULL(pOutputData, k);
       continue;
     }
@@ -535,7 +535,7 @@ int32_t concatWsFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *p
     bool hasNull = false;
     for (int32_t i = 1; i < inputNum; ++i) {
       if (colDataIsNull_s(pInputData[i], k) ||
-          GET_PARAM_TYPE(&pInput[i]) == TSDB_DATA_TYPE_NULL) {
+          IS_NULL_TYPE(GET_PARAM_TYPE(&pInput[i]))) {
         hasNull = true;
         break;
       }
@@ -1221,8 +1221,8 @@ int32_t timeDiffFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *p
       if (IS_VAR_DATA_TYPE(type)) { /* datetime format strings */
         int32_t ret = convertStringToTimestamp(type, input[k], TSDB_TIME_PRECISION_NANO, &timeVal[k]);
         if (ret != TSDB_CODE_SUCCESS) {
-          colDataAppendNULL(pOutput->columnData, i);
-          continue;
+          hasNull = true;
+          break;
         }
       } else if (type == TSDB_DATA_TYPE_BIGINT || type == TSDB_DATA_TYPE_TIMESTAMP) { /* unix timestamp or ts column*/
         GET_TYPED_DATA(timeVal[k], int64_t, type, input[k]);
@@ -1247,8 +1247,8 @@ int32_t timeDiffFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *p
         } else if (tsDigits == TSDB_TIME_PRECISION_NANO_DIGITS) {
           timeVal[k] = timeVal[k];
         } else {
-          colDataAppendNULL(pOutput->columnData, i);
-          continue;
+          hasNull = true;
+          break;
         }
       }
     }